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My furnace isn't working 100%. Sometimes it works fine, but occasionally (every few days) it doesn't ignite. I find the house cold, and the furnace vent blower running (not the main fan but the smaller fan inside the door), and I can see the igniter glowing through the little window that looks into the furnace, but sometimes the pilot light (the small flame that starts before the main flame) doesn't light. What should I check? |
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When the thermostat calls for heat, a series of events has to happen in the furnace for you to get heat. There's a blower fan that moves fresh air from the outside into the furnace, and then out the exhaust. That fan comes on first, and there's a rubber hose that runs from the housing for that fan to a sensor. The furnace waits until it senses a negative pressure in that hose before proceeding to the next step (so if the ignitor or pilot light never comes on, it could be because that fan is dying but that doesn't sound like the problem described). Next, the furnace turns on an igniter, which you should see glowing in the furnace, and then a small amount of gas - a pilot light. The furnace will then wait for the pilot to ignite and get confirmation of that from another sensor. Some furnaces have a sensor that looks for the glowing igniter. So in this case, the problem could be that the furnace doesn't think the igniter is on, or the gas isn't on. If you hear a click from the gas valve after the blower has been on a few seconds, that's the furnace turning on the gas to the pilot. If you don't hear the click, then I'd check the furnace logic board and its connections to the gas valve .. if you do hear a click but the pilot isn't lighting then it's probably the gas valve or the connection from there to the inside where the pilot flame is. (I'm no expert, but this is the troubleshooting I went through with the furnace guy when I had this problem). |
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